To cancel your AOL account, call 1-888-265-8008.
You can also mail AOL at PO Box 65100 / Sterling, VA 20165-8800 or FAX 703-433-7283. Specify that you're cancelling, give your full name, phone number, address and signature, and either the primary billing contact's AOL screenname or the last four digits of the current payment method. Make sure they give you a confirmation number. And if AOL continues billing you, contact the webmaster at AOL Watch.